This invention relates to devices and methods to insert position sensors into an anatomical body. More particularly, the present invention relates to a device and method for registering a position sensor inserted in an anatomical body.
Position sensors have been increasing in accuracy and decreasing in size. This has made position sensors for use in tracking portions of an anatomical body during surgical procedures more feasible.
However, in order to accurately track areas of interest in an anatomical body, it is necessary to rigidly fix the position sensor near or at a location of interest in the anatomical body. It is also necessary to then register the position sensor with the anatomical body. A position sensor is registered to an anatomical body by correlating the position of the position sensor in the anatomical body to the determined position of the position sensor in the frame of reference. At that time, the location of interest in the anatomical body can be tracked in a fixed frame of reference, such as the operating room frame of reference, by determining the position of the position sensor.
A number of position sensors have been used in the past. Recently, magnetic sensor coils or fibre optic sensors that are reasonably small, and therefore can be substantially unobtrusively inserted into an anatomical body, have been successfully used.
However, the prior art suffers from the disadvantage that it is difficult to register the position sensors to the anatomical body. Methods for registering the position sensor in the anatomical body have included obtaining an image of the anatomical body after insertion of the position sensor and attempting to register the position sensor to the anatomical body from the acquired image. However, this suffers from the disadvantage that the position sensor is not always easily identifiable in the acquired image. Furthermore, while it may be possible to determine the position of the position sensor in the anatomical body, sufficient information may not be available from the image to determine and register both the position as well as orientation of the position sensor. Because of this, it may not be possible to determine all of the degrees of freedom, such as movement along the x, y, z axes, as well as three orientation coordinates, namely pitch, yaw and roll.
In some embodiments, it may be desirable that the position sensor be permitted to move relative to the anatomical body. However, in most cases, it is preferred that there be no relative movement between the position sensor and the location of interest in the anatomical body. Most prior art devices and methods for registering the position sensor in an anatomical body suffer from the disadvantage that there may be relative movement between the position sensor and the anatomical body. Accordingly, in addition to a method and device for accurately registering the position of the position sensor in an anatomical body, there is a need in the art for a device and method to reliably fix the position sensor to the anatomical body, thereby avoiding relative movement during the procedure. There is also a need in the art for reliable devices and methods to insert the position sensor into the anatomical body.
Accordingly, it is an object of this invention to at least partially overcome the disadvantages of the prior art. Also, it is an object of this invention to provide an improved type of device and method that facilitates simple and accurate registration of a position sensor within an anatomical body. It is also an object of this invention to provide an improved type of device and method to minimize relative movement between the position sensor and the anatomical body.
Accordingly, in one of its aspects, this invention resides in an apparatus insertable into an anatomical body, said apparatus comprising an insertable portion for holding a position sensor that can transmit a signal indicative of its position in a frame of reference; fiducial markings on the insertable portion, said fiducial markings being detectable by an imaging modality when the insertable portion is inserted in the anatomical body; wherein, after insertion in the anatomical body, the fiducial markings can be detected by the imaging modality to facilitate registration of the position sensor held in the insertable portion to the anatomical body.
In a further aspect, the present invention resides in a method of registering a position sensor to an anatomical body, said method comprising the steps of: fixing a position sensor to an insertable portion of an apparatus, said insertable portion having fiducial markings thereon; inserting the insertable portion of the apparatus to a location of interest in the anatomical body; and detecting the fiducial markings on the insertable portion of the apparatus to facilitate registration of the position sensor in the insertable portion to the anatomical body.
In a further aspect, the present invention resides in a device for facilitating tracking of an apparatus in an anatomical body, said device comprising an insertable portion for holding a position sensor that can transmit a position signal indicative of its position in a frame of reference; wherein the apparatus can insert the insertable portion into the anatomical body, and, the position signal transmitted from the position sensor indicates the position of the apparatus near the position sensor.
In one aspect, the apparatus comprises a fixing mechanism for releasably fixing the insertable portion of the apparatus to the anatomical body at a location of interest. The fixing mechanism can be any type of mechanism that can releasably and rigidly fix the insertable portion to the anatomical body, such that the insertable portion will not become easily displaced during the procedure. In one embodiment, the fixing mechanism comprises a screw that screws into a part of the anatomical body, or, at least one barb that can become fixed to the anatomical body near the location of interest.
The fixing mechanism may also comprise an inflatable member that inflates when the insertable portion is at the location of interest. More preferably, the inflatable member has lobes that can inflate to fix the catheter, such as in a passageway near the location of interest, while still permitting fluid flow around the apparatus, such as a catheter, and through the passageway.
In a further preferred embodiment, the fixing mechanism comprises a plurality of movable fingers having gripping elements. The movable fingers have a collapsed configuration where the gripping elements are near the apparatus, such as a catheter or a needle, and permit insertion of the catheter into the anatomical body and near the location of interest. The movable fingers also have a deployed configuration where the gripping elements engage a surface of a passageway in the anatomical body to fix the insertable portion to the anatomical body near the location of interest, but permit fluid flow around the apparatus and through the passageway.
One advantage of the present invention is that the fiducial markings on the insertable portion permit the position, and preferably orientation, of the insertable portion to be accurately determined with respect to the anatomical body. As the position of the position sensor with respect to the insertable portion, and therefore the fiducial markings, is known, the position sensor can then be registered to the anatomical body by correlating the position of the fiducial markings in the images to the determined position of the position sensor in the fixed frame of reference.
A further advantage of the present invention is that the fixing mechanism preferably substantially rigidly fixes the insertable portion of the apparatus to the anatomical body. In this way, once the position sensor has been registered, relative movement between the anatomical body and the position sensor is decreased.